I am learning basic PHP from a book, and from what I read, = is an assignment operator, and == is a comparison operator. So...
$x = 5;
$x == 5: true
...makes sense. However, the book gives an example which confuses me:
if (++$x == 10)
echo $x;
Why ==? Aren't we trying to say "if ++$x equals 10, then echo $x"...? Then that would seem like: if (++$x = 10). The former would be like asking a question inside a conditional statement, which would be illogical or redundant.
== means equality, so the conditional reads as:
If pre-incremented $x equals 10, echo $x
Single = is assignment, where a variable is set to contain a value:
$word = 'hello';
$number = 5;
// etc.
echo "I said $word $number times!";
Regarding the increment opperators:
You'll see things like ++$x and $i-- as you learn PHP (and/or other languages). These are increment/decrement operators. Where they're positioned in relation to the variable they're operating on is important.
If they're placed before the variable, like ++$x, it's a pre-increment/decrement. This means the operation is performed before anything else can be done to the variable. If it's placed after, like $x++, it's a post-increment/decrement, and it means that the operation is performed afterward.
It's easiest to see in an example script:
$x = 5;
echo ++$x; // 6
echo $x++; // ALSO 6
echo $x; // NOW 7